U.S. Pat. No. 4,966,689 issued Oct. 30, 1992 issued to R. Wark et al. describes a self-cleaning grate assembly which is used as a size-based sorting device for lump coal. The device segregates coal according to size so that oversize coal lumps can be directed to a crusher for further size reduction. Devices of this type are used in systems for supplying pulverized coal to a combustion chamber in an electrical utility plant.
Because lump coal tends to get jammed between the bars of the sizing grate, it has been found desirable or necessary to clean the grate from time to time. This is accomplished by passing the bars of a pivotally displaceable cleaning comb upwardly through and between the spaced bars of the sizing grate so as to dislodge jammed lumps and send them in the direction of the crusher. The '689 patent, the disclosure of which is incorporated herein by reference, discloses such a cleaning comb, and an actuator for causing periodic operation of the cleaning comb.